Seeking a little advice. Hopefully one of you can help. Sorry this is a bit long. I am a new Betta owner and still learning.

A little background:

Bubbles is in a 2.5 gallon tank. While I have a heater, it has been warm here this past 2 weeks and Bubbles' tank is maintaining a temp between 76-78. Sometimes goes up to 80 but it's rare. It's filtered and has a good PH.

Last week I left town for 6 days. While I am fully aware I made some mistakes, I have learned from them. Before I left I did a 50% water change in his tank. About 2 days before that, I did a 100% water change. While gone, I left the filter running and put one of those auto-feeding cubes in his tank. (that is a mistake IMO that I learned from.) It was warm while I was gone, so I don't think his tank's temp changed much.

When I came home, Bubbles was NOT doing well. He was floating on his side. He'd get himself upright and try to swim, but would just end up floating back up to the top and then back on his side. I thought FOR SURE he was a goner and honestly prepared myself for him not being alive the following morning.

I did a water change feeling there was probably too much ammonia in the tank from the auto feeder. I also put some Betta Revive in the tank when I placed him back in. I also put a little bit of aquarium salt. When I woke up the next morning, he was back to swimming normally around the tank. He still had a little bit of a tilt as he swam, but that went away through out the day.

It's been 3 days since this has happened. He seems MUCH better. He built his biggest bubble nest the night before last. Just seems happy as a clam. :)

I do think he has some minor fin rot, which I am asking your opinion on. I have been treating it as fin rot with Mardel Maracyn. The other thing is he has a small white spot on him. Looking close, it looks like a scale that isn't laying flat but I am not 100% sure. I'm wondering what you all think it is. Sorry it's hard to see in the pictures. It's a hard picture to take. :(

I wish I had better pictures. He's great about posing but then quickly moves once I click the button. It's like he knows I am taking pictures!

We all make mistakes but what is important is that we learn from them and move on......just as you are doing....

You did the correct thing by making that water change when you did and now I would recommend that you continue with the water changes.
He most likely has some ammonia burns and he may develop some scar tissue depending on how bad the burns.
With the opening from the burns he is at risk of a secondary infection and the best way to prevent that is with 100% daily water changes, but since you have a filter you could do 50-80% daily and see how he looks, if the fins start to look worse you may want to move him to a small QT container and make 100% daily water changes with aquarium salt 1tsp/gal for 10 days and then switch to daily without the salt.

I worry about doing 100% water changes daily as it stresses him out so much. So what I have been doing is 1 day I will do a 100% water change, the next a 50%, then the next day a 100%....etc.

Yesterday when I did the 100%, I added the salt and I am still putting the medicine in. While I know it's only been a few days...I still don't see much progress with his tail. I wish I would see signs of healing.

How long does it take for fin rot to heal if you follow the right steps? What will be the first signs I will see? His little tail looks so shredded. I just could kick myself for doing this to him. Such a huge mistake and now he is paying the price.

IMO/E-100% daily water changes are a big healing of fins, the fish usually will get use to the 100% water changes and not stress too much, each fish can be different though.
I see re-growth with that method within a day or so, my main breeder(my avatar) had a chunk taken out of his anal fin last week and I already have over 2cm of new growth, its white in color and no secondary infection and I had to wait 5 day to even start treatment due to spawning at the time.
Your method of 100% and 50% should be okay, the point being clean water and the correct amount of salt to make a difference.